Differential turnover of Nup188 controls its levels at centrosomes and role in centriole duplication

Abstract

NUP188 encodes a scaffold component of the nuclear pore complex (NPC) and has been implicated as a congenital heart disease gene through an ill-defined function at centrioles. Here, we explore the mechanisms that physically and functionally segregate Nup188 between the pericentriolar material (PCM) and NPCs throughout the cell cycle. Pulse-chase fluorescent labeling approaches indicate that Nup188 populates centrosomes with newly synthesized protein that does not exchange with NPCs even after mitotic NPC breakdown. In addition, the steady-state level of Nup188 at centrosomes is controlled by the sensitivity of the PCM pool, but not the NPC pool, to proteasomal degradation. Proximity-labeling and super-resolution microscopy supports that Nup188 interacts with components of PCM including Cep192 and the centriolar satellite component, PCM1. Consistent with this, Nup188 plays a role in centriole duplication at or upstream of Sas6 loading. Together, our data establish Nup188 as a functional component of PCM and potentially provides insight into the pathogenesis of congenital heart disease.

Exportins can inhibit major mitotic assembly events in vitro: membrane fusion, nuclear pore formation, and spindle assembly

“…A steep biochemical gradient of RanGTP exists across the nuclear membrane with the concentration of RanGTP high in the nucleus and low in the cytosol [12,13]. This gradient is set up by RCC1, the GTP-exchange factor for Ran, which is an exclusively chromatin-localized protein [14][15][16][17][18][19][20][21][22][23][24]. RCC1 activates RanGDP by exchanging its GDP for GTP, but can do so only in the vicinity of the chromosomes.…”